My amp usually has a little bit of white noise to it, just a bit of hiss. Normal thing, right? But what hits me is that the loudness of the hiss changes a lot. IE when I turn my guitars volume down, it hisses for a while, then the hiss gets louder, then quieter again, and so on. While playing, the loudness is constant.

Is this an issue, or is this normal?
It really depends, If you can post a video clip showing the noise and showing the loudness of your playing it really helps. Please do talk in the video as it will give us a reference point for loudness.
I can't really record it, but it's not like it bothers me. I'm just curious to know if noise is ok to vary. Maybe the wall voltage changes a bit? Sometimes the noise just goes away completely and I found it interesting
does it change if you touch the guitar strings or electronics?

Are you using single coil or humbucker pickups? 

Does this happen at home or anywhere you try your rig?

Are there any pedals in the chain?
Last edited by Gab_Azz at May 21, 2017,
It happens even with the guitar's volume down when the guitar is on a stand.
Active emg hamburgers.
I've noticed it both at home and at our rehearsal room, where I can crank it louder.
I have a tuner, wah, and a tubescreamer in the chain but I keep everything off. (even the TS)
No by touching I mean you place your fingers or hand on either the strings, bridge or any metal knob or switch on your guitar. This is a way to identify bad earthing. To make sure that the noise is not coming out of any pedal, remove them from your signal chain for a couple of days as see what happens.
Touching it doesn't change anything. Firstly, active pickups need to grounding to the strings, secondly it would produce hum, not a white noise kind of thing.

At today's rehearsal the noise went quite insane with the variations, like a pc fan turning on and off. I took a look to see if my power tubes aren't redplating or something, and the noise went away.

The varying noise also occurs when I take the cable out of the amp, so only the preamp's own noise comes through
get a 12ax7 and try replacing the preamp tubes one at a time. This should not be very expensive and should not require bias.
I'll have to order one online, no nearby stores have them. I'll report back a
Problem fixed! I replaced v1 with a tung sol and v2 with an electro harmonix. It's quiet now, and sound way better than on stock tubes